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Old 07-15-2013, 08:40 PM   #1
Join Date: Nov 2012
Location: Kansas
Posts: 27
Coolant mystery

About a month ago, I noticed my 2000 was running warm (not in the red yet or smoking, but overhot). It has a 4.0 engine in it. I added water and replaced the radiator cap as the seal was slightly stiff on the old one. I filled the overfill bottle to the correct mark. I checked the manual and it said to check the overfill bottle monthly which was new to me as I've never had a vehicle I had to monitor the fluid that closely. Anyway, I've now had to add fluid (probably a pint each time) to get the bottle back to the fill line about every 2 weeks and I'm concerned that coolant seems to just be disappearing. Jeep has not overheated since I've been monitoring it. Jeep runs smooth as silk. No white rings at the fill cap or dip stick. No smell of burning antifreeze. No white exhaust. Jeep kept on garage floor so no sign of any fluid leaks. I just changed the oil today and no sign of antifreeze in the oil. So no indications of any sort that I have any seal leaks. Is this normal? Its in the 80-90 degree temps but does the coolant evaporate from the overfill bottle that much? I've never had a vehicle lose a pint of fluid every 2 weeks before but the Jeep shows no signs of leaks, nor coolant in the oil, nor coolant burning in the exhaust. Jeep has 90k on it.

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Old 07-16-2013, 03:50 PM   #2
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Join Date: Apr 2012
Posts: 2
Mine is doing the exact same thing. I have no idea where it's going. As far as I know it's not leaking on the ground as I check often but is constantly falling below the full line. Mine is also a 2000 4.0. Weird..

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Old 07-16-2013, 03:57 PM   #3
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Join Date: Jun 2011
Location: Bay Area, CA
Posts: 505
It sounds like a problem with the head that they used on 2000-01 4.0L engines. Search 0331 head and you will find many people with this same problem. There is most likely a crack in the head between I believe cylinders 3 and 4
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Old 07-16-2013, 04:12 PM   #4
Join Date: Jul 2013
Posts: 1
I also have just started to have this problem I thought I was not vigilant enough and now i am watching things a little closer nice to know I'm not the only one have you found a solution
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Old 07-16-2013, 04:56 PM   #5
Join Date: Nov 2012
Location: Kansas
Posts: 27
Why am I not finding any sign of a cracked head in the oil or the exhaust then? Is it a small enough leak that it all burns up with no odor? Wouldn't the jeep not run smooth if it had a cracked head?
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Old 07-16-2013, 05:03 PM   #6
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Join Date: Dec 2012
Location: Chester Virginia
Posts: 2,958
I would say you should check all the freeze plugs in the block. I know mine is a 2.5 but I do have a couple of them leaking. Drive me crazy as well until I figured it out. Now it is on the list of things to do one day. If they are leaking it may be evaporating from the heat on the block before it has the chance to make it to the ground. That is the case with mine. If you look closely at them though you will see a residue almost like a corroded battery terminal. If you see that then they are leaking.

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